FR3031595A1 - METHOD AND KIT FOR THE DETERMINATION OF IRON IONS IN LUBRICATING COMPOSITIONS - Google Patents

Abstract

The present invention relates to a method for the determination of iron, especially ferric and ferrous ions, by spectrophotometry, contained in a used lubricant composition, in particular a lubricant composition of a marine engine. The present invention also relates to a kit for implementing this method.

Description

Method and kit for the determination of iron ions in lubricating compositions The present application relates to a method for the determination of corrosive iron, ie ferric and ferrous ions, in used lubricating compositions, more particularly in the compositions Used engine lubricants, especially marine engine. The present application also relates to a kit for implementing this method. Engines, in particular marine engines, undergo significant constraints during their operation, in particular frictional stress, and are subject to corrosion, in particular, for example in the case of marine engines, due to the presence of sulfur in the fuel oil. which is converted into sulfuric acid during combustion. Lubricating compositions are generally used to reduce these stresses. By these phenomena, including friction and corrosion, metal particles or contaminants, including particulate iron, ferric ions and ferrous ions, are released in these lubricant compositions. These metal contaminants, if they are present in too large a quantity, can cause a modification of the properties of said lubricating compositions and therefore of their performances and be damaging for the engine (notably a decrease in the service life). There is therefore an interest in assaying these metal contaminants in the lubricating compositions to determine the state of degradation of these compositions and thus the optimal moment of the change thereof. In addition, the determination of these metallic contaminants also makes it possible to determine the importance of these phenomena, in particular of friction and corrosion, and to make decisions for the maintenance and the preservation of the lubricated material, in particular the adjustment of the quantity of lubricating composition to introduce. Laboratories propose to perform analyzes of samples of used lubricant compositions to determine the amounts of metal contaminants. However, this requires the sending of samples, a significant implementation time and consequently delayed actions.

There is therefore an interest in providing a method for the determination of iron, in particular ferric and ferrous ions resulting from corrosion, in used lubricating compositions and a kit adapted to the implementation of this method, which can be used on place, which are fast and reliable.

3031595 2 There are colorimetric tests, the determination of a concentration range of iron is visually compared with reference samples. However, these methods are unreliable. It is also known from WO2006127098 a method for analyzing the amount of iron contained in a used lubricating composition. However, this method allows the determination of the total iron contained in said lubricant composition, that is to say both the particulate iron resulting from friction phenomena, ferric and ferric ions resulting from corrosion. It is therefore not possible, by this method, to determine the real impact of each of these two phenomena taken separately and, for the operators, to act accordingly. One of the objectives of the present invention is therefore to provide a method for "on-site" determination of iron, ferric ion and ferrous ions, especially resulting from the corrosion of the metal parts of the engines, in the used lubricating compositions, in particular recovered from bottom of the engine cylinders. Another object of the present invention is to provide such a method for which the preparation of the sample for the assay is simple and fast. Still another object of the present invention is to provide such a method which is fast, preferably less than 10 minutes, reliable and reproducible. Another objective of the present invention is to provide a method allowing a measurement accuracy of plus or minus 10 ppm and allowing a measurement in the range 0 to 900 ppm. Yet another object of the present invention is to provide a kit for implementing said method, which is simple and fast to use. Still other objects will appear on reading the description of the invention which follows. All these objectives are fulfilled by the present invention which proposes a method of "on-site" measurement of iron ions, in particular ferric and ferrous ions, in lubricating compositions, especially used lubricating compositions, for example recovered at the bottom of the cylinders of motor, by photochemical measurement after reaction of the iron ions with a complexing agent of iron ions, the complexation reaction causing a color change that can be quantified by spectrophotometry.

The method for determining iron ions, in particular ferric and ferrous ions, in the lubricating compositions according to the present invention comprises the following steps: a) taking a sample of the lubricant composition to be analyzed, for example down the engine cylinders in a first container; B) Removal of the first container containing the sample to be analyzed on a magnet; c) Adding in a second container: a first aqueous reactive composition (CR1) comprising at least one agent for extracting ferric and ferrous ions from the oily phase to the aqueous phase; A second aqueous reactive composition (CR2) comprising at least one agent for reducing ferric ions (Fe3 +) to ferrous ions (Fe2 +); o a third reactive composition (CR3) comprising at least one destabilizing emulsion agent; and o a fourth reactive composition (CR4) in aqueous solution comprising a ferrous ion complexing agent, characterized in that this agent changes color upon complexation with the ferrous ions; and mixing; d) optionally, photochemical measurement of the absorbance of the mixture obtained in step c); E) taking a few drops of the lubricant composition contained in the first container, held in place on the magnet, and adding these few drops in the second container comprising the mixture of the first, second, third and fourth reactive compositions obtained in step c); f) stirring of the mixture obtained in step e); G) Photochemical measurement of the absorbance of the mixture obtained in step f); h) Determining the amount of ferrous ions in the lubricant composition from the measurements obtained in steps d) and g). The lubricating composition to be analyzed is preferably a used lubricant composition of the engine, preferably a marine engine lubricating composition, for example a ship engine or a hydroelectric power plant, etc. Preferably, the lubricating composition is a lubricating composition for a marine engine 2 times. Preferably, the lubricating composition to be analyzed is a used lubricant composition recovered at the bottom of the engine cylinders.

The lubricant composition of the present invention comprises at least one lubricating base oil. In general, the lubricating base oils may be oils of mineral, synthetic or vegetable origin, and mixtures thereof. The mineral or synthetic oils generally used belong to one of groups I to V according to the classes defined in the API classification (or their equivalents according to the ATIEL classification) as summarized below. The API classification is defined in the American Petroleum Institute 1509 "Engine Oil Licensing and Certification System" 17th edition, September 2012. The ATIEL classification is defined in "The ATIEL Code of Practice", Issue 18, November 2012. Content Content saturated sulfur viscosity Group I Mineral oils <90%> 0.03% 80 VI <120 Group II Hydrocracked oils 90% 0.03% 80 VI <120 Group III 90% 0.03% 120 Hydrocracked or hydro-isomerized oils Group IV PAO (Poly alpha olefins) Group V Esters and other bases not included in groups I to IV Groups Group I mineral oils may be obtained by distillation of selected naphthenic or paraffinic crudes followed by purification of distillates obtained by processes such as extraction by solvent, solvent dewaxing or catalytic, hydrotreatment or hydrogenation. Group II and III oils are obtained by further purification processes, for example a combination of treatment selected from hydrotreatment, hydrocracking, hydrogenation and catalytic dewaxing. Examples of Group IV and V synthetic base oils include polyisobutenes, alkylbenzenes and poly-alpha olefins such as polybutenes or esters. In lubricating compositions, the lubricating base oils may be used alone or in admixture. For example, a mineral oil can be combined with a synthetic oil. Two-stroke marine engine cylinder oils are typically characterized by a SAE-40 viscometric grade to SAE-60, typically SAE-50 equivalent to a kinematic viscosity at 100 ° C of between 16.3 and 21.9 mm2 / s measured according to ASTM D445. SAE-40 grade oils have a kinematic viscosity at 100 ° C of between 12.5 and 16.3 cSt measured according to ASTM D445. SAE-50 grade oils have a kinematic viscosity at 100 ° C between 16.3 and 21.9 cSt measured according to ASTM D445. SAE-60 grade oils have a kinematic viscosity at 3031595 at 100 ° C between 21.9 and 26.1 cSt measured according to ASTM D445. The lubricating compositions of the invention preferably have a kinematic viscosity measured according to ASTM D445 at 100 ° C ranging from 12.5 to 26.1 cSt, preferably from 16.3 to 21.9 cSt. To obtain such viscosity, the lubricating compositions of the invention may further comprise one or more additives. Typically, a conventional formulation of a lubricating composition for marine engines, preferably two-stroke, is SAE-40 to SAE-60, preferably SAE-50 (according to SAE J300 classification) and comprises at least 40% by weight of oil. lubricant base of mineral origin, synthetic or mixtures thereof, suitable for use for a marine engine. For example, a Group I lubricating base oil, according to the API classification, can be used for the formulation of a cylinder lubricant. Group I lubricating base oils have a Viscosity Index (VI) ranging from 80 to 120; their sulfur content is greater than 0.03% and their content of saturated hydrocarbon compounds is less than 90%.

The lubricating composition according to the invention may further comprise an additive selected from overbased detergents or neutral detergents. The detergents are typically anionic compounds having a long lipophilic hydrocarbon chain and a hydrophilic head, the associated cation is typically a metal cation of an alkali or alkaline earth metal. The detergents are preferably chosen from alkali metal or alkaline earth metal salts (in particular calcium, magnesium, sodium or barium), carboxylic acids, sulphonates, salicylates and naphthenates, as well as salts of phenates. These metal salts may contain the metal in an approximately stoichiometric amount relative to the anionic group (s) of the detergent. In this case, we speak of non-overbased or "neutral" detergents, although they also bring some basicity. These "neutral" detergents typically have a BN (Base Number or Index of basicity), measured according to ASTM D2896, less than 150 mg KOH / g, or less than 100 mg KOH / g, or even less than 80 mg KOH / g of detergent. This type of so-called neutral detergents can contribute in part to the BN of the lubricating compositions. For example, neutral detergents of carboxylates, sulphonates, salicylates, phenates, alkali metal and alkaline earth metal naphthenates, for example calcium, sodium, magnesium or barium, are used. When the metal is in excess (in excess of the stoichiometric amount relative to the anionic group (s) of the detergent), so-called overbased detergents are used. Their BN is high, greater than 150 mg KOH / g of detergent, typically ranging from 200 to 700 mg KOH / g of detergent, preferably from 250 to 450 mg KOH / g of detergent. The excess metal providing the overbased detergent character is in the form of oil insoluble metal salts, for example carbonate, hydroxide, oxalate, acetate, glutamate, preferably carbonate.

In the same overbased detergent, the metals of these insoluble salts may be the same as those of the oil-soluble detergents or may be different. They are preferably selected from calcium, magnesium, sodium or barium. The overbased detergents are thus in the form of micelles composed of insoluble metal salts maintained in suspension in the lubricating composition by the detergents in the form of oil-soluble metal salts. These micelles may contain one or more types of insoluble metal salts, stabilized by one or more detergent types. Overbased detergents with a single type of detergent soluble metal salt will generally be named after the nature of the hydrophobic chain of the latter detergent. Thus, they will be said phenate, salicylate, sulfonate, naphthenate depending on whether the detergent is a phenate, salicylate, sulfonate, or naphthenate respectively. The overbased detergents will be said to be of mixed type if the micelles comprise several types of detergents, different from each other by the nature of their hydrophobic chain. The overbased detergent and the neutral detergent may be selected from carboxylates, sulfonates, salicylates, naphthenates, phenates, and mixed detergents associating at least two of these types of detergents. The overbased detergent and the neutral detergent are in particular compounds based on metals chosen from calcium, magnesium, sodium or barium, preferentially calcium or magnesium. The overbased detergent may be overbased with metal insoluble salts selected from the group of alkali and alkaline earth metal carbonates, preferably calcium carbonate. The lubricating composition may comprise at least one overbased detergent and at least one neutral detergent as defined above. As mentioned above, in one embodiment of the invention, the lubricating composition has a BN determined according to ASTM D-2896 of at most 50, preferably at most 40, preferably at most 30 milligrams of potash per gram of lubricating composition, especially ranging from 10 to 30, preferably from 15 to 30, advantageously from 15 to 25 milligrams of potash per gram of lubricating composition. In this embodiment of the invention, the lubricating composition may not include alkali or alkaline earth metal based detergents overbased with carbonate metal salts.

In another embodiment of the invention, the lubricating composition has a BN determined according to the ASTM D-2896 standard of at least 50, preferably at least 60, more preferably at most 70, advantageously of 70 to 100.

The lubricating composition may also comprise at least one further additive selected from dispersants, anti-wear additives or any other functional additive. Dispersants are well known additives used in the formulation of lubricating composition, especially for application in the marine field. Their primary role is to maintain in suspension the particles present initially or appearing in the lubricant during its use in the engine. They prevent their agglomeration by playing on steric hindrance. They can also have a synergistic effect on the neutralization. The dispersants used as lubricant additives typically contain a polar group, associated with a relatively long hydrocarbon chain, generally containing from 50 to 400 carbon atoms. The polar group typically contains at least one nitrogen, oxygen or phosphorus element. The compounds derived from succinic acid are dispersants particularly used as lubrication additives. Especially succinimides, obtained by condensation of succinic anhydrides and amines, succinic esters obtained by condensation of succinic anhydrides and alcohols or polyols. These compounds can then be treated with various compounds including sulfur, oxygen, formaldehyde, carboxylic acids and compounds containing boron or zinc to produce, for example, borated succinimides or zinc-blocked succinimides. Mannich bases, obtained by polycondensation of phenols substituted with alkyl groups, formaldehyde and primary or secondary amines, are also compounds used as dispersants in lubricants. In one embodiment of the invention, the dispersant content may be greater than or equal to 0.1%, preferably 0.5 to 2%, advantageously 1 to 1.5% by weight relative to the total weight. of the lubricating composition. The antiwear additives protect the friction surfaces by forming a protective film adsorbed on these surfaces. The most commonly used is zinc di thiophosphate or DTPZn. This category also contains various phosphorus, sulfur, nitrogen, chlorine and boron compounds. There is a wide variety of anti-wear additives, but the most commonly used category is phospho-sulfur additives such as metal alkylthiophosphates, particularly zinc alkylthiophosphates, and more specifically zinc dialkyldithiophosphates or DTPZn. The preferred compounds are of the formula Zn ((SP (S) (01:11) (OR2)) 2, or R1 and R2 are alkyl groups, preferably having 1 to 18 carbon atoms. at levels of the order of 0.1 to 2% by weight relative to the total weight of the lubricating composition Amine phosphates, polysulfides, especially sulfur-containing olefins, are also commonly used antiwear additives. Lubricants for marine engines are also usually found in the presence of anti-wear and extreme pressure additives of the nitrogen and sulfur type, such as, for example, metal dithiocarbamates, in particular molybdenum dithiocarbamate, and glycerol esters are also anti-wear additives. Mention may be made, for example, of mono, di and trioleates, monopalmitates and monomyristates In one embodiment, the content of anti-wear additives ranges from 0.01 to 6%, preferably from 0.1 to 4% by weight relative to the total weight of the lubricating composition. The other functional additives may be chosen from thickening agents, anti-foaming additives to counteract the effect of detergents, which may be, for example, polar polymers such as polymethylsiloxanes, polyacrylates, anti-oxidant and / or anti-rust additives, for example organometallic detergents or thiadiazoles. These are known to those skilled in the art. These additives are generally present at a content by weight of 0.1 to 5% relative to the total weight of the lubricating composition.

Advantageously, in the method of the present invention, step b) makes it possible to obtain a deposit at the bottom of the first container of the particulate iron possibly contained in the lubricant composition to be analyzed and resulting from the friction of the engine parts. Particularly advantageously, the sampling of step e) is carried out on the supernatant, which makes it possible to assay only ferric and ferrous ions and thus to determine the extent of the single corrosion phenomenon. In the context of the present invention, the term "iron ion" denotes ferric ions and ferrous ions.

Lubricating compositions are generally composed of lubricating oils and additives and are therefore viscous and generally colored. It is thus not easy to carry out the colorimetric determination of iron ions directly in the lubricant composition. The present invention therefore proposes passing the iron ions in the aqueous phase. Advantageously, the first reactive composition (CR1) of the method according to the present invention comprises in aqueous solution at least one agent for extracting ferric and ferrous ions from the oily phase of the lubricating composition to the aqueous phase. The extraction agent makes it possible to pass all the ferric and ferrous ions from the oily phase of the lubricating composition to the aqueous phase, the water originating in particular from the composition CR1, in which the complexation with the complexing agent and the dosage. This extraction agent is in particular chosen from agents solubilizing ferric and ferrous ions and being immiscible with the lubricating composition. Among these extraction agents there may be mentioned acids, preferably acids with a pKa between -5 and +5, including sulfuric acid, nitric acid, hydrochloric acid, phosphoric acid, alone or in mixture. Preferably, the acid has a pKa of -3. The composition CR1 may further comprise other constituents, in particular additives which aid in the preparation of the composition and which advantageously make it possible to increase the speed of the analysis. Among these additives include co-solvents helping solubilize compounds of the reactive composition CR1, for example of the alcohol type, for example ethanol. In the second reactive composition (CR2) of the present invention, the ferric ion reducing agent to ferrous ions is preferably selected from the following reducing agents: hydroquinone, hydroxylamine hydrochloride, hydrazine, dithionite, alone or in combination with mixed. The reducing agent makes it possible to obtain a solution comprising only iron ions in a single form (entity) and consequently to have a more reliable and precise dosage.

The composition CR2 may further comprise buffer solutions making it possible to maintain the substantially stable pH, preferably between 2 and 7, more preferably between 2 and 3. Among the buffer solutions, mention may be made of basic solutions or of acid or their mixtures, for example solutions, especially concentrated of a preferentially weak acid and its conjugate base, salts, for example sodium salts such as sodium acetate, or their mixture. Preferably, the buffer solution is preferably chosen from sodium acetate and acid solutions, in particular acetic acid, glycine and hydrochloric acid solutions, ethanoacetic acid and sodium ethanoate solutions, or solutions of citric acid and sodium phosphate.

Preferably, the first reactive composition according to the present invention preferably comprises from 1 to 10% by weight of extraction agent. Preferably, the second reactive composition according to the present invention comprises from 1 to 15% by weight of reducing agent. In a particularly advantageous manner, the first and second reactive compositions can be mixed into a single aqueous reactive composition (CR1 ') then comprising at least one ferric and ferrous ion extraction agent from the oily phase to the aqueous phase, water derived in particular from the composition CR1 ', and at least one agent for reducing ferric ions (Fe3 +) to ferrous ions (Fe2 +). Preferably, the reactive composition CR1 'comprises from 1 to 15% by weight of reducing agent and from 1 to 10% by weight of extraction agent. This reactive composition (CR1 ') may further comprise other constituents, especially additives assisting in the preparation of the composition and advantageously to increase the speed of the analysis. Among these additives, mention may be made of co-solvents which aid in the solubilization of the compounds of the reactive composition CR 1 ', for example of the alcohol type, for example ethanol and / or buffer solutions making it possible to maintain the substantially stable pH, preferably between 2 and 7, more preferably between 2 and 3, among the buffer solutions, mention may be made of base or acid solutions or mixtures thereof, for example solutions, in particular concentrated solutions of a weak acid and its conjugated base, salts , for example sodium salts such as sodium acetate, or their mixture. Preferably, the buffer solution is preferably chosen from sodium acetate and acid solutions, in particular acetic acid, glycine and hydrochloric acid solutions, ethanoic acid and sodium ethanoate solutions or solutions of citric acid and sodium phosphate. Preferably, the reactive composition (CR 1 ') of the invention comprises ethanol, sulfuric acid, hydroxylamine hydrochloride and sodium acetate dissolved in water. The third reactive composition (CR3) of the method according to the invention comprises at least one destabilizing emulsion agent. The first, second and fourth reactive compositions and the reactive composition CR1 'are aqueous compositions. In admixture with the lubricating composition these aqueous compositions can form an emulsion. The third reactive composition therefore advantageously makes it possible to break the emulsion thus obtained and consequently to allow a better phase shift. Thus, the third reactive composition of the method according to the invention advantageously facilitates and accelerates the passage of ferric and ferrous ions from the oily phase of the lubricating composition to the aqueous phase brought by the first, second and second and fourth reactive compositions or by the reactive composition CR1 '. Advantageously, the destabilizing agent is composed of water-immiscible compound. The destabilizing agent of the invention is preferably chosen from primary or secondary alcohols (C4 to O10), alone or as a mixture. Preferably, the destabilizing agent of the invention is chosen from isoamyl alcohol, octan-1-ol, octan-2-ol, alone or as a mixture, preferably isoamyl alcohol. Preferably, the third reactive composition according to the method of the present invention comprises from 20 to 100% by weight of emulsion destabilizing agent.

The third reactive composition of the present invention may further comprise additives, for example when the destabilizing agent has a too high flash point, the third reactive composition according to the invention may comprise co-solvents making it possible to reduce the flash point. of the composition. Among these co-solvents, mention may be made, for example, of light petroleum distillates, preferably comprising less than 2% of aromatic compounds, such as, for example, hydrocarbons, preferably C9 to C16 hydrocarbons, for example n-C9 alkane. C16, C9-C16 isoalkane, C9-C16 cyclic hydrocarbons. The fourth reactive composition (CR4) of the method according to the present invention comprises a complexing agent for ferrous ions. This complexing agent is chosen from the complexing agents ferrous ions and whose complexation is at the origin of a color change that can be detected by measuring the absorbance of the solution obtained by a spectrophotometer. The measured absorbance can then be related to the content of ferrous ions, and therefore iron ions, of the sample analyzed, expressed in ppm. Preferably, this complexing agent is selected from ferrozine, ferene, phenanthroline and its derivatives, for example bathophenantroline, bipyridine, thioglycolic acid, salt R-nitroso (sodium salt of 3-hydroxy-acid). 4-nitroso-2,7-naphthalenedisulfonic acid), potassium ferricyanurate (potassium hexacyanoferrate (III)), 2,4,6-tripirydyl striazine (TPTZ). Preferably, the complexing agent is selected from TPTZ, potassium ferricyanurate or R-nitroso salt. Preferably, the complexing agent is the salt R-nitroso. Preferably, the fourth reactive composition comprises from 0.5 to 5% by weight of the complexing agent. Preferably, the reactive composition comprises 1% by weight of the complexing agent.

The assay method of the present invention is a colorimetric assay method employing a measurement of the absorbance of the solution obtained by complexing the complexing agent with the ferrous ions by UV-visible spectrometry, using a spectrophotometer, preferably an electron spectrophotometer. Thus, the absorbance measurements of steps d) and g) are performed using a spectrophotometer, preferably an electron spectrophotometer. The absorbance measurement by the spectrophotometer is based on Beer Lambert's law. An intensity incident light 10 passes through the aqueous solution to be analyzed, a portion of this light is absorbed by the solution, the resulting intensity 1 is transmitted through the solution. The absorbance (A) of the solution is then determined by the following relationship: (±) = log (A) 1 It is possible to relate the absorbance to the concentration of ferrous ions in the solution with the aid of a calibration curve giving a line connecting the absorbance to the concentration of ferrous ions of solution of known concentration. The electron spectrophotometer is calibrated beforehand with this calibration curve and the measured absorbance makes it possible to determine the amount of ferrous ions in ppm in the sample to be analyzed.

In a first embodiment, a blank measurement of the absorbance can be performed on a container comprising the mixture of the four reactive compositions defined above. This blank measurement is then considered as a reference in the spectrophotometer and each of the measurements performed on the compositions obtained in step (f) will be compared to this blank value to give the actual value of the absorbance as explained below. . In a second embodiment of the invention, and in order to obtain a reliable and fair value of the absorbance and therefore indirectly of the concentration of ferrous ions, a blank is made to take into account the influence of the second container and first, second, third and fourth reactive compositions on the measurement of absorbance.

For this, a step d) of measuring the absorbance is performed on the mixture obtained in step c) in the second container. By difference between the absorbance obtained in step g) and that obtained in step c), the actual absorbance of the solution obtained in step f) is obtained and the corresponding amount of iron ions can thus be determined. Particularly advantageously, the electronic spectrophotometer is programmed to discriminate between the absorbances measured in steps d) and g) and then the corresponding iron ion concentration in the solution to be analyzed in ppm. In step g), the second container is placed in the spectrophotometer so that the incident light emission passes only through the aqueous phase. As will be seen later, the spectrophotometer preferably has a receiving zone 3031595 13 of the adapted sample, preferably at a suitable angle, so that the incident light emission passes only through the aqueous phase. . In a particularly advantageous manner, all of these steps d), g) and h) are implemented directly by the electronic spectrophotometer which is programmed for this purpose. Preferably, the stirring of step f) is carried out by inverting the container at least 5 times, for example 10 times. After stirring, the container is directly introduced into the spectrophotometer. Preferably, the measurement during step g) is carried out in less than 10 minutes after introduction of the container into the spectrophotometer, preferably the measurement is carried out 5 minutes after the introduction of the container into the spectrophotometer, this time representing the time required for the complexing agent complexing reaction with the ferrous ions. Preferably, the first, second, third and fourth reactive compositions are each introduced in a proportion of 5 to 10 ml in the second container. Preferably, the first, second, third and fourth reactive compositions are each introduced at a rate of 5 ml into the second container. Preferably, the third and fourth reactive compositions as well as the CR1 'composition are each introduced in a proportion of 5 to 10 ml in the second container. Preferably, the third and fourth reactive compositions as well as the composition CR1 'are each introduced at the rate of 5 ml into the second container. In another embodiment, the first, second and third reactive compositions may be contained in a single reactive composition (CR) previously prepared.

Preferably 1 to 10 drops, preferably 3 drops, ie about 0.075 g or 100 μl, of lubricating composition to be analyzed are introduced in step e) into the second container. The method according to the present invention can be repeated as many times as there are samples to be analyzed. In this case, there will be as many first and second containers as 3031595 14 lubricating compositions to be analyzed. Particularly advantageously, if step d) is implemented, it will be convenient to do steps d) and g) for each sample to be analyzed one after the other and not to do steps d) for each of the samples to be analyzed then the steps g) for each of the samples to be analyzed, in fact, the spectrophotometer is preferably parameterized to compare each of the mixtures obtained in steps c) and f). In a particularly advantageous manner, the method according to the present invention is reliable, it makes it possible to determine from 0 to 900 ppm of iron in the samples, preferably from 50 to 700 ppm. Advantageously, the method according to the invention is simple and fast and does not require any special knowledge of the operator. Advantageously, the method according to the invention makes it possible to obtain a result on the amount of iron ions in a lubricant composition used in less than 10 minutes and with an accuracy of the order of plus or minus 10 ppm. Particularly advantageously, the method of the present invention does not require the heating of the samples to be analyzed, nor the digestion of the particulate iron.

The present invention also relates to a kit for carrying out the method described above. This kit comprises: a first aqueous reactive composition (CR1) comprising at least one ferric and ferrous ion extracting agent from the oily phase of the lubricating composition to the aqueous phase; a second aqueous reactive composition (CR2) comprising at least one agent for reducing ferric ions (Fe3 +) to ferrous ions (Fe2 +); a third reactive composition (CR3) comprising at least one destabilizing emulsion agent; A fourth reactive composition (CR4) in aqueous solution comprising a ferrous ion complexing agent characterized in that this agent changes color upon complexation with the ferrous ions; a spectrophotometer, preferably an electronic spectrophotometer; optionally at least one first container; At least one second container; Optionally at least one device (D1) for sampling the lubricating composition to be analyzed; a device (D2) for each of the samples of the first, second, third and fourth reactive compositions; 5 a magnetic support; at least one device (D3) for sampling a few drops of the lubricant composition to be analyzed during step e). CR1, CR2, CR3 and CR4 are as defined above.

The spectrophotometer, preferably an electron spectrophotometer, comprises a light emitting device, for example a light-emitting diode; a photoelectric sensor; a receiving zone of the second container; Absorbance data processing software for conversion to ferrous ion concentration in ppm. Preferably, the receiving zone of the second container is positioned between 10 and 50 mm, preferably between 15 and 30 mm, for example 24 mm from the bottom of the second container and oriented at an angle of 35 to 75 °, preferably cb. 50 to 70 °, for example 60 ° to allow a measurement of the absorbance only in the aqueous phase of the mixture obtained in step f) in which there is the colored complex formed between the complexing agent and the ferrous ions.

Preferably, the first container is made of plastic or glass, preferably plastic. It possibly includes a plug. Preferably, the kit comprises at least as much first container as samples of lubricating composition to be analyzed. Indeed, the engines comprise between 4 and 14 cylinders, so there is at least between 4 and 14 samples of lubricant composition to be analyzed at the same time (a sample of lubricant composition per cylinder). Preferably, there is at least one first container, preferably there is between one and 50 first containers, for example between 5 and 40 first containers.

Preferably, the second container is a tube-shaped container with a stopper, preferably a test tube with a stopper. It may be plastic or glass, preferably glass. Preferably, the kit comprises as many second containers as samples of lubricating compositions to be analyzed. The kit thus comprises between 1 and 100 second containers, for example between 10 and 80 seconds containers, for example 50 second containers.

The first and second containers may be glass or plastic containers, they may be disposable or cleanable. Preferably, in the context of the invention the first and second containers are disposable.

Preferably, the device (D1) for taking the lubricant composition to be analyzed is a syringe, preferably a disposable plastic material. The kit may comprise as many devices (D1) as lubricant compositions to be analyzed, preferably the kit comprises from 1 to 100 devices (D1), preferably from 10 to 80, for example 50. Preferably, each of the devices ( D2) are syringes, preferably of disposable plastic material. The kit may comprise from 3 to 18 devices (D2), preferably from 3 to 6 devices (D2).

Preferably, the magnetic support is a support for receiving the first container comprising the lubricating composition to be analyzed and comprising a magnet at its bottom. Preferably, the magnetic support is a rack comprising from 1 to 50, preferably 7 locations for receiving the first containers. Preferably, the magnetic support 20 is in two parts, a lower portion including the locations for receiving the first containers, each of the locations comprising a magnet, and an upper portion including locations for the second containers, the locations of the lower portion. and the locations of the upper part preferably being placed opposite each other in order to quickly and simply identify the lubricating compositions to be analyzed. Preferably, the device (D3) for taking a few drops of the lubricant composition to be analyzed in step e) is a pipette, preferably a disposable plastic material or a positive displacement micropipette, for example 100 μl. , for example of the type Microman Gilson or Transferpettor Brand. There may be at least as much device (D3) as lubricant compositions to be analyzed. For example, the kit may comprise from 1 to 50 devices (D3), preferably 50 devices (D3). Particularly advantageously, the kit according to the invention can be stored in a trunk or suitcase and is therefore easily transportable.

3031595 17 Figure (1) represents a kit according to the invention. Figure (2) shows a magnetic support according to the invention.

The kit of Figure (1) comprises: a magnetic support (1) comprising locations (2) each comprising a magnet and intended to receive first containers (3) and locations (4) for receiving second containers ( 5); first containers (3); Second containers (5); a reactive composition (CR1 ') (6); a reactive composition (CR3) (7); a reactive composition (CR4) (8); an electron spectrophotometer (9) comprising a location (10) for receiving the second containers, preferably at an angle of 35 to 75 °, preferably 50 to 70 °, per temple of 60 ° to the body of the spectrophotometer; at least one device (D3) (11); and at least three devices (D2) (12).

Figure (2) shows a magnetic support (1) comprising locations (2) each comprising a magnet and for receiving first containers (3) and locations (4) for receiving second containers (5).

The present invention will now be described by way of nonlimiting example of implementation of the method and the kit of the invention. Example 30 The operator starts the spectrophotometer. a) The operator collects the lubricant compositions to be analyzed in first containers (3) and places these containers in the locations (2) comprising magnets of the magnetic support (1), whereby the particulate iron possibly present in the lubricating composition The analyzer is drawn down the container near the magnet. (B) The operator then adds, using three separate devices D2 (12) each of the reactive compositions CR1 '(6), CR3 (7) and CR4 (8), into as many second containers (5) as There are oils to analyze. The contents of the second containers are mixed by inverting the second containers (5). All the second containers (5) are arranged in the locations (4) of the magnetic support (1). c) The operator then introduces one of the second containers (5) in the location (10) of the spectrophotometer (9) and measures the absorbance of the solution contained in the second container (5). d) This second container (5) is then replaced in one of the locations (4) of the magnetic support (1) and the operator adds three drops, using a device D3 (11), a lubricating compositions for analysis contained in one of the first containers (3). To do this the operator must be careful not to introduce the device D3 at the bottom of the container (3) so as not to take particulate iron possibly present at the bottom of the container (3). After adding the lubricating composition, the operator notes a color change resulting from the reaction between the iron ions and the complexing agent of the reactive composition (CR4). e) The container (5) is then mixed by inverting it 10 times and then introduced into the location (10) of the spectrophotometer (9). f) The container (5) is left for 5 minutes in the location (10) of the spectrophotometer (9) before starting the measurement of the absorbance of the solution contained in said second container (5). g) The spectrophotometer then calculates the difference between the absorbance measurement when the container (5) comprises only the reactive compositions CR1 ', CR3 and CR4 and the measurement of the absorbance when the lubricating composition has been added to the composition. container (5). h) From the measurement obtained in g) the spectrophotometer determines the amount of iron ions contained in the lubricant composition to be analyzed. Steps c) to h) are then repeated for each of the lubricant compositions to be analyzed. 30

Claims (11)

CLAIMS 1. A method for determining iron ions, in particular ferric and ferrous ions, in lubricating compositions, comprising the following steps: a) taking a sample of the lubricating composition to be analyzed in a first container; b) removing the first container containing the sample to be analyzed on a magnet; c) Adding in a second container: a first aqueous reactive composition (CR1) comprising at least one agent for extracting ferric and ferrous ions from the oily phase to the aqueous phase; a second aqueous reactive composition (CR2) comprising at least one agent for reducing ferric ions (Fe3 +) to ferrous ions (Fe2 +); o a third reactive composition (CR3) comprising at least one destabilizing emulsion agent; and o a fourth reactive composition (CR4) in aqueous solution comprising a ferrous ion complexing agent, characterized in that this agent changes color during its complexation with ferrous ions; and mixing; d) optionally, photochemical measurement of the absorbance of the mixture obtained in step c); e) taking a few drops of the lubricant composition contained in the first container, held in place on the magnet, and adding these few drops in the second container comprising the mixture of the first, second, third and fourth reactive compositions obtained in the first step c); f) stirring of the mixture obtained in step e); g) photochemical measurement of the absorbance of the mixture obtained in step f); h) Determining the amount of ferrous ions in the lubricant composition from the measurements obtained in steps d) and g). 2. Method according to claim 1, wherein the extraction agent is chosen from agents solubilizing ferric and ferrous ions and being immiscible with the lubricating composition, for example acids, in particular sulfuric acid, nitric acid, hydrochloric acid. phosphoric acid, alone or in admixture. 3031595 20 3. The method of claim 2, wherein the extracting agent is sulfuric acid. 5 4. A method according to any one of claims 1 to 3, wherein the ferric ion ferric ion reducing agent is selected from hydroquinone, hydroxylamine hydrochloride, hydrazine, dithionite, alone or in admixture. 5. The method of claim 4, wherein the ferric ion reducing agent 10 is ferrous ion hydroxylamine hydrochloride. 6. A method according to any one of claims 1 to 5, wherein the destabilizing agent is selected from primary or secondary alcohols (C4 to 010) immiscible with water, alone or in mixture. 15 7. The method of claim 6, wherein the destabilizing agent is isoamyl alcohol. 8. Method according to any one of claims 1 to 7, wherein the complexing agent is selected from the complexing agents ferrous ions and whose complexation is at the origin of a color change that can be detected by measuring the absorbance of the solution obtained by a spectrophotometer, preferably the complexing agent is chosen from ferrozine, ferene, phenanthroline and its derivatives, for example bathophenantroline, bipyridine, thioglycolic acid, salt R- nitroso (sodium salt of 3-hydroxy-4-nitroso-2,7-naphthalenedisulfonic acid), potassium ferricyanurate (potassium hexacyanoferrate (III)), 2,4,6-tripirydyl-s-triazine ( TPTZ). 9. The method of claim 8, wherein the complexing agent is Rnitroso salt. 30 10. Method according to any one of claims 1 to 9, wherein the first and second reactive composition are included in an aqueous reactive composition CR1 '. 3031595 21 11. Kit for carrying out the method according to any one of claims 1 to 10 comprising: a first aqueous reactive composition (CR1) comprising at least one agent for extracting ferric and ferrous ions from the oily phase of the lubricating composition to the aqueous phase as defined in claims 1 to 3; a second aqueous reactive composition (CR2) comprising at least one agent for reducing ferric ions (Fe3 +) to ferrous ions (Fe2 +) as defined in claims 1, 4 and 5; a third reactive composition (CR3) comprising at least one emulsion destabilizing agent as defined in claims 1, 6 and 7; a fourth reactive composition (CR4) in aqueous solution comprising a ferrous ion complexing agent, as defined in claims 1, 8 and 9, characterized in that this agent changes color when complexed with ferrous ions; A spectrophotometer, preferably an electron spectrophotometer; optionally at least one first container; at least one second container; optionally at least one device (D1) for sampling the lubricating composition to be analyzed; One device (D2) for each of the samples of the first, second, third and fourth reactive compositions; a magnetic support; at least one device (D3) for sampling a few drops of the lubricant composition to be analyzed during step e).